The invention relates to a loudspeaker system comprising an enclosure which accommodates a loudspeaker device and a bass-reflex port, which port has two open ends and means for the suppression of noises.
A bass-reflex port is basically an open tube or pipe by means of which an internal volume of a loudspeaker enclosure communicates with an environment outside the enclosure, one open end being situated inside the enclosure and one open end being situated outside the enclosure. Such a port enhances the reproduction of sound in the lower range of the frequency spectrum. The operation of the bass-reflex port is based on the Helmholtz resonator principle, which is known per se, the frequency of the reproduced sound being dependent on the volume of the enclosure, the length and the cross-sectional dimension of the port and the velocity of sound. Small loudspeaker enclosures require a port of comparatively small cross-section. However, in a small enclosure, it is necessary that per unit of time the same amount of air flows through the port in order to obtain the same sound pressure at or near the Helmholtz frequency as in a large enclosure. This means that the flow velocity of the air in the port is comparatively high for a small enclosure. It has been found that when known bass-reflex ports are used, a high sound level at or near the Helmholtz frequency is attended by noises, i.e. undesired sounds.
U.S. Pat. No. 5,109,422 discloses a loudspeaker system, which comprises an enclosure with a loudspeaker and a bass reflex port made up of a plurality of parts. This bass reflex port comprises a visco-elastic part formed by two rubber outer cylinders disposed in line with one another and an air-permeable part formed by a felt inner cylinder, the inner cylinder extending between and for a substantial part in the outer cylinders, to which it is connected.
The bass-reflex port used therein serves to counteract undesired sounds, particularly duct resonant sounds. However, the multi-part port also forms a drawback of the known loudspeaker system because the manufacture of such a bass-reflex port is rather laborious owing to the necessity of positioning various parts relative to one another and subsequently securing them to one another.
It is an object of the invention to improve the known loudspeaker system so as to counteract undesired sounds in an effective and simple manner.